Nonlinear vibration analysis of full-ceramic bearing-rotor systems with a ball defect considering thermal deformation

Full-ceramic bearings exhibit high stiffness and low deformation, but their brittle ceramic balls easily develop surface defects under cyclic stresses. To understand the influence of ball defects on the full-ceramic bearing-rotor system, an impact force excitation function is proposed, which considers both thermal deformation and ball defects. The defect size changes the contact deformation in the bearing, which consequently changes the contact force. Moreover, the impact force also affects the frictional force. These factors are incorporated into the dynamic model. The model describes a full-ceramic bearing-rotor system with a defect-ball. This study examines the effects of speed, thermal effects and defect dimensions on the nonlinear vibration of the system. Experimental validation is conducted using simultaneous temperature and vibration testing. The results indicate that thermal deformation expands the instability zone at high speeds; it also decreases the transition of motion states. As the ball defect size increases, the amplitudes of the relevant frequencies f b and f c and their combined frequencies in the spectrum increase. The experimental and simulation results agree, and the amplitude error of the ball impact frequency is 6.08%. This study provides a framework for analysing the dynamics of full-ceramic bearing-rotor systems.